This application relates generally to communications networks, and more particularly, to determining electrical properties of multi-wire communication lines.
Recently, there has been an increased demand for the subscriber lines of plain old telephone services (POTS""s) to carry high-speed digital signals. The demand has been stimulated by home access to both the Internet and distant office computers. Both types of access typically employ a POTS line as part of the path for carrying digital signals.
POTS""s lines were built to carry voice signals at audible frequencies and can also carry digital signals as tone signals in the near audible frequency range. Modern digital services such as ISDN and ADSL transmit data at frequencies well above the audible range. At these higher frequencies, POTS""s lines that transmit voice signals well may transmit digital signals poorly. Nevertheless, many telephone operating companies (TELCO""s) would like to offer ISDN and/or ADSL data services to their subscribers.
Telephone lines between a TELCO switch and subscribers"" premises are frequent sources of poor performance at the high frequencies characteristic of ISDN and ADSL transmissions. Nevertheless, high cost has made widespread replacement of these subscriber lines an undesirable solution for providing subscribers with lines capable of supporting ISDN and ADSL. A less expensive alternative would be to repair or remove only those subscriber lines that are inadequate for transmitting high-speed digital data.
To limit replacement or repair to inadequate lines, TELCO""s have placed some emphasis on developing methods for predicting which subscriber lines will support data services, such as ISDN and ADSL. Some emphasis has been also placed on predicting frequency ranges at which such data services will be supported. Some methods have also been developed for finding faults in subscriber lines already supporting data services so that such faults can be repaired.
Current methods for predicting the ability of subscriber lines to support high-speed digital transmissions are typically not automated, labor intensive, and entail test access at multiple points. Often, these methods entail using skilled interpretations of high frequency measurements of line parameters to determine data transmission abilities. At a network scale, such tests are very expensive to implement.
The present invention is directed to overcoming or, at least, reducing the affects of one or more of the problems set forth above.
In a first aspect, the invention provides a method of determining a physical structure of a subscriber line. The method includes searching a reference set for a match between the subscriber line and a model line of the reference set and identifying that the subscriber line has a specific physical structure. The match is based on electrical properties of the lines. The act of identifying is responsive to finding a match with one of the model lines that has the specific physical structure.
In a second aspect, the invention provides a method of qualifying a subscriber line for a data service. The method includes searching a reference set of model lines for a best match to a subscriber line by comparing sets of electrical properties and determining that the subscriber line has a specific physical structure. The act of determining is responsive to the best matching model line having the specific physical structure. The method also includes disqualifying the subscriber line for the data service, in part, in response to determining that the specific physical structure corresponds to a disqualified line.
In a third aspect, the invention provides a method of providing a data service. The method includes searching for a match between electrical properties of a subscriber line and a model line of a reference set and determining whether the subscriber""s line is qualified for the data service. The act of determining is based in part on whether the best matching model line has one of a bridged tap and a mixture of gauges. The method also includes performing a business action in response to determining that the subscriber""s line is qualified.
In a fourth aspect, the invention provides a data storage device that stores an executable program of instructions for causing a computer to perform one or more of the above-described methods.
Various embodiments use test accesses, which provide data on low frequency electrical properties of subscriber lines, to make predictions about high frequency performance.